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Understanding Cataract, Its Symptoms and Treatments
Cataract is a common cause of visual impairment in the elderly but can also affect a small number of younger individuals. The number of cataract patients is greater than the number of glaucoma, macular degeneration and diabetic retinopathy patients combined. It is common in people over 65 years of age.
What is a cataract?
The eye is like a camera where the retina is the film at the back, and the lens is positioned at the front of the eye, just behind the pupil. A cataract is a clouding in the lens of eye. The lens in your eye focuses light and is constructed of proteins and fluid. The proteins are arranged in a parallel fashion to allow the light to pass through the lens without interruption. The pupil dilates and contracts to control the level of light reaching the retina and the lens adjusts automatically to allow you see objects clearly at various distances.
As one ages, cataract begins when some of the parallel proteins become disorganised causing a small part of the lens to become cloudy and this becomes larger as the cataract progresses. Eventually the whole lens becomes opaque and blocks off light to the retina causing a major reduction in vision. In most medically advanced countries a cataract operation is readily available allowing vision to be restored quickly.What are the different types of cataract?
Subcapsular occurs at the back of the lens typically afflicting people with diabetes, retinitis pigmentosa and those on steroid therapy.
Nuclear develops in the lens central zone or nucleus. This is the commonest form of cataract and occurs with age.
Cortical this type develops around the len's border like the spokes of a wheel. It progresses towards the centre of the lens eventually blocking off the vision.
What are the symptoms?
The blurring of vision is gradual, hardly affecting the sight at first. It would seem like looking through an opaque glass at times. Light from the sun, a lamp or oncoming headlights cause dazzle and in daylight colours seem faded. Patients often remark that colours are more vibrant in one eye than the other.
Symptoms and their onset may vary depending on the cataract type. With nuclear cataract for example there may be an improvement in reading and close work for many months or even years, due to the development of short sightedness, but eventually this will also deteriorate as the cataract progresses. Subcapsular cataract can occur rapidly and affect the vision in a shorter period of time than other types of cataracts.
It is best to visit an eye doctor if you suspect you are developing a cataract.
What are the causes?
Despite studies, it is unknown exactly why cataracts form as the lens ages. While the factors are being gradually identified, some doctors believe that diet with high antioxidants (beta-carotene, vitamins A, C and E, and selenium) may help keep cataracts at bay. However none of these theories has been conclusively proven.
- Ultraviolet light eye doctors advise the use of sunglasses and wide-brim hats to protect against UV light exposure which is suspected to be associated with cataract development.
- X-ray exposure according to a 2005 Iceland study, airline pilots and astronauts are at higher risk of developing nuclear cataract due to cosmic radiation exposure.
- Steroids, diuretics and major tranquilisers- some of these are suspected to cause cataract but further proof is yet to be established. Steroid use in particular is associated with cataract development.
- Other risk factors too much salt, alcohol, air pollution and smoking are also associated with cataract formation. Again all these processes are difficult to prove. There is evidence to show that diabetics are more prone to cataract formation.
How is cataract treated?
At an early stage cataract can be treated by changing the power of your glasses. This can go on for years at a time and an annual review is indicated. Later as the cataract becomes more opaque the only effective treatment is surgery.
When should I have my cataract removed?
This depends on your circumstances. If you are a car driver then surgery is indicated at a much earlier stage than for people who don't drive. In Ireland, a binocular vision of 6/12, adequate contrast sensitivity and a normal field of vision is necessary for driving. Driving is extremely important to most people and no one wants to lose their independence, so if the above parametres are being threatened by cataract formation then early surgery is indicated. However, if you don't drive or happy to give it up and have adequate vision to carry out your normal activities then cataract surgery can be postponed indefinitely or until you ask for it to be performed. There can be many years difference in the timing of cataract surgery depending on your life-style or circumstances.
What does a cataract operation entail?
In most cases cataracts surgery is performed under local anaesthetic which may just be drops alone, or an injection around the eye (a bit like for a filling at your dentist's), but often a combination of both of these methods is used. You are admitted to the hospital at 8 am and you will usually be home by lunchtime. Nowadays the procedure is straight forward and takes about 20 minutes, nonetheless great skill is required to perform one of these operations which involves a team of doctors and nurses in a theatre setting, where important precautions are taken to prevent infection. The media often portray this operation as a simple procedure which it is definitely is not, but in skilled hands it is very successful in most cases. During the operation a tiny plastic lens (an IOL) is placed in the eye to help focus the light post-operatively. Prior to surgery a special test called biometry is carried out to decide on the power of the IOL to be inserted.
Will I need to use glasses following surgery?
You will be asked by your surgeon if you would like to have your eyes focussed for the distance following surgery. Most people wish for this, but if you are short-sighted your surgeon will probably suggest that enough short-sightedness is allowed to exist post-operatively, so that you may continue reading without glasses. If you are a golfer, or other sportsperson, then you may wish to be able to see in the distance without glasses whether you are short-sighted or not. This all needs to be discussed with your surgeon prior to the operation. If you are happy wearing bifocals or varifocals then you may wish to continue with these following surgery for convenience sake and it is worth mentioning this to your eye doctor before your operation.
Further improvements are being developed on surgical procedures and IOLs. Presbyopia-correcting IOLs for instance may allow clear vision at any distance. Another IOL type, one that can block retina-damaging UV and UVB rays, is being developed. In future in Ireland cataract surgery will be laser assisted and machines for this are currently being fine-tuned in trials around the world.
Most patients recover very quiclky following cataract surgery. A plastic eye-guard is worn at night for a couple of weeks to prevent inadvertant rubbing of the eye during sleep. Many recommence driving after one to two weeks.
You will be required to use post-operative steroid/antibiotic drops for 4 weeks to prevent infection and to settle port-operative inflammation. Usually you return for follow up one week after surgery but if undue soreness or blurring occurs a few days following discharge, then return to the clinic or hospital immediately for a check up.
Most patient have returned to normal activities such as work after two weeks.